1. Field of the Invention
The present invention relates to a pump unit including a plurality of hydraulic pump bodies disposed in parallel to each other.
2. Related Art
A pump unit including a plurality of hydraulic pump bodies disposed in parallel to each other has been conventionally used in various fields (for example, refer to Japanese patent application unexamined publication JP 2003-291674).
The conventional pump unit includes first and second pump shafts, first and second hydraulic pump bodies respectively driven by the first and second pump shafts, a pump case, and a center section (or a port block) connected to the pump case so as to form a pump accommodating space for accommodating the first and second hydraulic pump bodies in cooperation with the pump case.
The conventional pump unit is configured so that one pump shaft of the first and second pump shafts acts as an input shaft operatively connected to a driving power source and the other pump shaft is operatively connected to the one pump shaft through a gear transmission mechanism.
Specifically, the one pump shaft is supported by a pump housing formed by the pump case and the center section in a rotatable manner around its axis line in a state that one end of the one pump shaft is extended outward from the pump housing.
The conventional pump unit includes, in addition to the above components, the gear transmission mechanism operatively connecting the first and second pump shafts, and a lid member connected to the pump housing so as to form a gear accommodating space for accommodating the gear transmission mechanism in cooperation with the pump housing.
The conventional pump unit has an advantage of transmitting rotational power from the driving power source to both of the first and second pump shafts by operatively connecting the driving source to the first pump shaft. However, on the other hand, it invites a problem of cost increase because it requires the gear transmission mechanism and the lid member to be included.
Another problem caused by the conventional pump unit is that the stored oil inside of the pump accommodating space and the gear accommodating space causes resistance against rotation of the gear transmission mechanism since the conventional pump unit is configured so that the pump accommodating space and the gear accommodating space are fluidly connected to each other, resulting in worsened transmission efficiency from the driving power source to the first and second pump shafts.
In consideration of the above prior art, it is an object of the present invention to provide a pump unit including a plurality of hydraulic pump bodies disposed in parallel to each other, the pump unit capable of achieving cost reduction as much as possible while preventing transmission efficiency from being deteriorated.